One example of a scanning probe microscope is an atomic force microscope (AFM) which measures atomic forces that operate between a probe (cantilever) and the surface of a specimen (non-conductive specimen such as an insulator and biological or organic molecules) to observe the shape of the specimen's surface.
FIG. 5 shows a schematic view of the configuration of a scanning probe microscope. FIG. 6 shows a plan view of a previous scanning probe microscope. FIG. 7 shows a sectional view taken along line C-C in FIG. 6. FIG. 8 shows a sectional view taken along line D-D in FIG. 6.
The scanning probe microscope 130 includes a cantilever support part 2 which supports cantilever 1, displacement measurement parts 3, 4, 5 and 6 for measuring the displacement of cantilever 1, a disk-shaped carrying stage 140 on which a specimen S is placed, a piezo scanner (scanning means) 107 on whose upper surface the carrying stage 140 is installed, and a controller (not illustrated) (see for example Patent Literature 1).
The displacement measurement parts are not illustrated in FIG. 6 and FIG. 8.
The controller stores different measurement modes such as contact mode, constant height mode, non-contact mode and dynamic mode.
The “contact mode” is the mode wherein—while the controller performs a feedback control so that the reaction force between cantilever 1 and specimen S is kept constant—the surface of specimen S is scanned, and height is measured based on the amount of feedback. The “constant height mode” is the mode wherein—while the height of cantilever 1 is kept constant—the surface of specimen S is scanned, and height is measured based on the amount of deflection of cantilever 1. The “non-contact mode” is the mode wherein—while performing feedback control so that the force of attraction is kept constant between specimen S and the cantilever 1 oscillating near the resonance point—the surface of specimen S is scanned, and height is measured based on the amount of feedback. Furthermore, the “dynamic mode” is a mode wherein—while performing feedback control so that the reaction force is kept constant between specimen S and the cantilever 1 oscillating near the resonance point—the surface of specimen S is scanned, and height is measured based on the amount of feedback.
Cantilever support part 2 includes a cantilever 1, a light-transmissive, cylindrical support part body 21, a light-shielding support frame 22 for holding the support part body 21 and a rod-shaped support lever 24 for positioning the cantilever 1.
The cantilever 1 is in the form of a plate with, for example, a length of 100 μm and a thickness of 0.8 μm with a pointed probe disposed at its tip. The other end of the cantilever 1 is fixed to the bottom edge face of the cantilever support part 21 by means of a fixing jig 23. Any fixing means such as a screw, spring or a like mechanism may be used as the fixing jig 23. In other words, a person performing the measurement can select and use a cantilever 1 out of a plurality of types of cantilevers to suit the specimen S or the purpose of the measurement.
The support part body 21—further described below in detail—includes two holes that penetrate it in the vertical direction. Formed in one of the penetrating holes is an infusion tube 12 for introducing a fluid 10. Formed in the other penetrating hole is a discharge tube 13 for discharging the fluid 10.
The support frame 22 includes a light-shielding, square-shaped upper surface and a light-shielding, cylindrical sidewall that surrounds the perimeter of the upper surface. Formed in the center of the upper surface is a circular opening where the support part body 21 is attached. A support lever 24 is attached to the sidewall so that it protrudes, horizontally outward. Furthermore, a portion of the sidewall on the support lever 24 side of the support frame 22 is cut out so that the positional relationship between the cantilever 1 and specimen. S can be viewed from the support lever 24 side.
The displacement measurement parts 3, 4, 5 and 6 include a laser light source 3 for emitting a laser beam, a beam splitter 4 for directing the emitted laser beam to the back surface (upper surface) of the cantilever 1, a mirror 5 for adjusting the direction of the laser beam that is reflected by the back surface of the cantilever 1 and a photodiode 6 for detecting the reflected laser beam. With this configuration, the afore-described various measurement modes use the fact that the direction of the laser beam reflected by the back surface of the cantilever 1 changes depending on the deflection (displacement) of cantilever 1. This fact is used to detect the shape of the surface of specimen S.
When seen in a plan view, the carrying stage 140 has a circular shape with a diameter of, for example, 15 mm and a thickness when viewed in a side elevation of 4 mm. Furthermore, a magnet 71 is disposed inside the carrying stage 140. Because of this, when a specimen container 11 is placed on the upper surface of the carrying stage 140, the force of attraction between a magnetic material 72 of the specimen container 11 and the magnet 71 in the carrying stage 40 causes the specimen container 11 to be fixed to the carrying stage 140. This is described in greater detail below.
The carrying stage 140 is integrally mounted to the upper surface of a piezo scanner 107 which uses piezo devices to scan the carrying stage 140 in the X-, Y- and Z-directions. This means that specimen S that is placed on the carrying stage 140 is scanned in the X-, Y- and Z-directions.
The shape of the surface of a specimen S that is located in air can be observed by placing the specimen S directly on the upper surface of the carrying stage 140. However, to observe the shape of the surface of a specimen S that is present in a solution (acidic or alkaline solution), a specimen container 11 containing a fluid 10 and specimen S is placed on the upper surface of the carrying stage 140.
The specimen container 11 such as the aforesaid comprises a circular, light-transmissive bottom surface 18, a cylindrical, light-transmissive sidewall 19 that surrounds the perimeter of the bottom surface 18 and a disk-shaped magnetic material 72 that is attached to the back side of the bottom surface 18. A person taking a measurement selects a particular specimen container 11 out of a choice of many so that the diameter of the bottom surface 18 and the height of the sidewall 19 of the specimen container 11 fit the outer diameter of the support part body 21, the inner diameter of the support frame 22, the size of the specimen S and the amount of movement of the specimen container 11.
The method for measuring and observing the shape of the surface of a specimen S that is present in a fluid 10 using a scanning probe microscope 130 is described next.
First, based on the size and the like of the specimen S, a person taking the measurement selects a specimen container 11. The specimen S is then placed on the bottom surface 18 of the specimen container 11. The specimen container 11 is then placed on the upper surface of the carrying stage 140. When this is done, the attractive force between the magnetic material 72 of the specimen container 11 and the magnet 71 that is disposed in the carrying stage 140 fixes the specimen container 11 to the carrying stage 140.
Next, after selecting a cantilever 1, the person taking the measurement uses the fixing jig 23 to fix the cantilever 1 to the cantilever support part 2. The cantilever support part 2 is then installed to a support rod 22. The support lever 24 is then operated to position the cantilever 1 inside the specimen container 11.
The person taking the measurement then introduces a fluid 10 through the infusion tube 12. The level of the fluid in the specimen container 11 should high enough so that at least the specimen S and the cantilever 1 are immersed in the fluid 10. Because the piezo scanner 107 may be damaged if the fluid 10 spills onto it, this operation should be performed with care so that the fluid 10 does not spill out of the specimen container 11.
A person taking the measurement uses the piezo scanner 107 to scan the specimen S in the X-direction, Y-direction and the Z-direction while measuring the displacement of cantilever 1 using the displacement measurement parts 3, 4, 5 and 6. Care is required in this operation so that fluid 10 does not spill out of the specimen container 11 by, for example, bumping the specimen container 11 against the support part body 21 or the support frame 22.
After the displacement of the cantilever 1 is measured, the person taking the measurement discharges the fluid 10 through the discharge tube 13.
Lastly, the person taking the measurement operates the support lever 24 and moves the cantilever 1. The specimen container 11 is then removed from the upper surface of the carrying stage 140. During this operation as well, since all of the fluid 10 cannot be discharged through the discharge tube 13, care is necessary to not spill any of the fluid 10 remaining inside the specimen container 11.